Rebuilt my Q-jet, need some help now.

1085 Views 12 Replies 4 Participants Last post by SWHEATON, May 27, 2008

1971 Chevelle

Discussion Starter · May 26, 2008

I rebuilt my Quadrajet to Cliff's specs for my car(Trans-am). I believe the float is set right. Its got a Carter 120gph fuel pump. New jets and rods. New accel. pump, basically all new inside.
When I first started driving it would buck when trying to cruise at light throttle. I turned to APT screw out until that quit.
The problem I am having is with the Secondaries. If I drive along at 30 in first gear it will spin the tires like crazy, but then if I shift into second and get back on it, it bogs. Or if I try to punch it in 2nd or 3rd gear at say 2500rpm it will bog but it sounds like the secondaries are opened, then when it gets up around 4 or 5K it will pull like a freight train. The same happens in 4th at 3000rpm.

Would the spring that controls the butterflies in the air horn need tightened more? Or would it be the choke pull off the lets them open, Cliff gave me a new pull-off in the kit. Any suggestions? It gets very expensive testing this at $4.30/gal for premium. Fun,

But expensive.

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gnicholson

· #2 · May 26, 2008

how big is the restriction on the choke pull off? what 2nd rods? have you done any mods to the pull over circuit at the air valve

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gnicholson

· #4 · May 26, 2008

some people call it a secondary accel. pump. small discharge holes either just above or below the air valve depending on carb. it helps to enlarge the discharge size if it bogs on initial opening of the sec.. start with your airvalve spring adjusted to3/4 turn after contact and go an 1/8 turn at a time tighter. what rod and hanger do you have? the pull off might have to large of a restriction. raising the rods with a higher hanger might help as would a richer rod. tell me what you have and ill try to help

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gnicholson

· #6 · May 26, 2008

those are the ones. all the things i mentioned affect performance during sec opening

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gnicholson

· #7 · May 26, 2008

also , make sure the rod from the choke p/o has a very small amount of clearance when vacuum is applied to the p/o. sometimes this rod is bent to long and allows the airvalve to move before it can be controlled by the p/o

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gnicholson

· #9 · May 26, 2008

a large opening on the pull off will allow it to open too fast. usually on the nipple where the vacuum hose goes. if the hole has been opened up to the tube i.d. the you will have no dampening effect. the discharge holes for the airvalve can be enlarged .002 or .003 to help pull a little more fuel like an accel pump nozzle in a holley for instance:beers:

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